Preparation And Photocatalytic Properties Of TiO₂/Thin-layer Phlogopite-vermiculite Nanocomposite

Based on the Mosaic structure of industrial vermiculite,high expansion factor expanded vermiculite was prepared by chemical microwave/roast method and its best preparation technology and expansion mechanism were studied.Using high expansion factor expanded vermiculite as raw material,thin-layer phlogopite-vermiculite nanosheet was prepared by stirring pretreatment and ultrasonic stripping with high speed homogenizer.The differences between high expansion vermiculite prepared by chemical-microwave method and chemical-roasting method respectively during liquid phase ultrasonic peeling were revealed to provide a matrix for the preparation of photocatalytic composites.TiO₂/TPVN photocatalytic composite was prepared by co-precipitation method using TiOSO₄ as raw material and TPVN-R as matrix.The effects of the amount of TiOSO₄,the pH of the composite reaction and the calcination temperature on the photocatalytic performance of the composite were investigated.The composite was doped with Fe³⁺to test its photocatalytic degradation efficiency in the visible range.The results show that there are inlaid structures of phlogopite,hydro-phlogopite and vermiculite in the Industrial Vermiculite of Yuli,Xinjiang.After being modified by the mixed solution of hydrogen peroxide and oxalic acid and heated at high temperature,the sample expanded violently to form HEV sample.In the expansion process,hydrogen peroxide played the main role,while oxalic acid played the secondary role.The maximum expansion rate of HEV-R sample was 67 times.The maximum expansion rate of HEV-M sample was 43 times.The relatively complete layered structure of HEV still existed with good strippability.The peeling effect and yield of TPVN-R samples were mostly better than those of TPVN-M samples,and the TPVN-M/TPVN-R samples obtained by liquid phase peeling method showed obvious sheet structure.The sheet diameter was 0.3-1 nm,the thickness was less than 10 nm,and the maximum diameter-thickness ratio was 128 times.The thermal stability of TPVN sample was the same as that of non-exfoliated industrial vermiculite.TPVN had strong dispersing ability for nano-TiO₂ particles,and its strong adsorption promoted the contact probability of target degradants with TiO₂ particles.TPVN could effectively hinder the crystal phase transition of nano-TiO₂.The degradation rate of MB dye with initial concentration of100 mg/L reached 88.96%by 25 mg of TiO₂/TPVN photocatalytic composite.After Fe³⁺doping,the absorption edge of the sample gradually redshifted obviously,and the absorption band edge was larger than the maximum absorption wavelength?387 nm?of nano-TiO₂.The band gap width of the samples was also narrowed obviously,and the photocatalytic activity was improved obviously under visible light.When the molar ratio of Fe³⁺doping is 1%,the total removal rate of 100 mg/L MB solution by the sample under visible light could reach72.01%.The preparation process of high expansion rate expanded vermiculite can greatly improve the utilization rate of Industrial Vermiculite and effectively reduce the production cost of expanded vermiculite.Successful preparation of TPVN provides a possibility for large-scale and low-cost preparation of two-dimensional nanomaterials.The preparation of photocatalytic composites proves the application value of exfoliated minerals in the field of environmental treatment.It is of great significance for exploring the application of expanded vermiculite in the field of photocatalysis,expanding its application field,and realizing the nanocrystallization and multi-functionalization of industrial vermiculite.